linux-kernel - Re: [PATCH v2 4/4] media: tc358746: add Toshiba TC358746 Parallel to CSI-2 bridge driver

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Message-ID: <Yyhonw7SEjkAPivN@paasikivi.fi.intel.com>
Date:   Mon, 19 Sep 2022 13:03:27 +0000
From:   Sakari Ailus <sakari.ailus@...ux.intel.com>
To:     Laurent Pinchart <laurent.pinchart@...asonboard.com>
Cc:     Marco Felsch <m.felsch@...gutronix.de>, mchehab@...nel.org,
        robh+dt@...nel.org, krzysztof.kozlowski+dt@...aro.org,
        kishon@...com, vkoul@...nel.org, hverkuil@...all.nl,
        jacopo@...ndi.org, kieran.bingham+renesas@...asonboard.com,
        linux-media@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-phy@...ts.infradead.org,
        kernel@...gutronix.de
Subject: Re: [PATCH v2 4/4] media: tc358746: add Toshiba TC358746 Parallel to
 CSI-2 bridge driver

On Mon, Sep 19, 2022 at 03:49:04PM +0300, Laurent Pinchart wrote:
> On Mon, Sep 19, 2022 at 12:39:35PM +0000, Sakari Ailus wrote:
> > > +	dev_set_drvdata(dev, tc358746);
> > > +	pm_runtime_set_autosuspend_delay(dev, 200);
> > > +	pm_runtime_use_autosuspend(dev);
> > > +	pm_runtime_enable(dev);
> > > +
> > > +	err = tc358746_init_hw(tc358746);
> > 
> > The driver depends on runtime PM being enabled but does not depend on
> > CONFIG_PM. I'd suggest to power the device on and only then enable runtime
> > PM. See
> > <URL:https://hverkuil.home.xs4all.nl/spec/driver-api/camera-sensor.html#power-management>.
> 
> Or simply depend on CONFIG_PM :-)

The user can still disable runtime PM.

I guess few do though. This should be addressed separately from this
driver, it'd be good to be able to deny that. In fact, no-one has ever
probably tested this for a large number of drivers and I guess it exists
just to have a way to disable runtime PM support in drivers that do not
work with it...

-- 
Sakari Ailus